https://gcc.gnu.org/g:b065e82ac0a5b02167043e7ef1bb7f512e81543f
commit b065e82ac0a5b02167043e7ef1bb7f512e81543f
Author: Ondřej Machota <ondrejmach...@gmail.com>
Date: Sun Mar 30 22:53:17 2025 +0200
rtl-ssa-dce: cleanup and comparsion with ud_dce
Diff:
---
gcc/dce.cc | 292 +++++++++++++++++++++++++++++----------------------------
gcc/passes.def | 3 +-
2 files changed, 153 insertions(+), 142 deletions(-)
diff --git a/gcc/dce.cc b/gcc/dce.cc
index bb7040ae653d..53934d19c0ac 100644
--- a/gcc/dce.cc
+++ b/gcc/dce.cc
@@ -578,6 +578,7 @@ reset_unmarked_insns_debug_uses (void)
}
/* Delete every instruction that hasn't been marked. */
+static bool inside_ud = false;
static void
delete_unmarked_insns (void)
@@ -585,6 +586,7 @@ delete_unmarked_insns (void)
basic_block bb;
rtx_insn *insn, *next;
bool must_clean = false;
+ bool any = false;
FOR_EACH_BB_REVERSE_FN (bb, cfun)
FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
@@ -653,9 +655,17 @@ delete_unmarked_insns (void)
}
else
/* Now delete the insn. */
+ if (inside_ud) {
+ debug(insn);
+ }
+ any = true;
must_clean |= delete_insn_and_edges (insn);
}
+ if (any && inside_ud) {
+ std::cerr << "\033[31m" << "ud was able to delete more insns..." <<
"\033[0m \n";
+ }
+
/* Deleted a pure or const call. */
if (must_clean)
{
@@ -809,6 +819,7 @@ fini_dce (bool fast)
static unsigned int
rest_of_handle_ud_dce (void)
{
+ inside_ud = true;
rtx_insn *insn;
init_dce (false);
@@ -829,6 +840,7 @@ rest_of_handle_ud_dce (void)
they are not bidirectional. */
df_remove_problem (df_chain);
delete_unmarked_insns ();
+ inside_ud = false;
fini_dce (false);
return 0;
@@ -1306,14 +1318,15 @@ public:
} // namespace
+// This struct could help to remove unordered_set for rtl ssa dce
struct offset_bitmap {
private:
const int m_offset;
sbitmap m_bitmap;
public:
- offset_bitmap(size_t size, int offset) : m_bitmap{sbitmap_alloc(size)} {}
- offset_bitmap(int min_index, int max_index) : offset_bitmap(max_index -
min_index, 0) {}
+ offset_bitmap(size_t size, int offset) : m_offset{offset},
m_bitmap{sbitmap_alloc(size)} {}
+ offset_bitmap(int min_index, int max_index) :
offset_bitmap(size_t(max_index - min_index), min_index) {}
void clear_bit(int index) {
bitmap_clear_bit(m_bitmap, index + m_offset);
@@ -1332,26 +1345,6 @@ struct offset_bitmap {
}
};
-bool sets_global_register(rtx_insn* insn) {
- rtx set = single_set(insn);
- if (!set)
- return false;
-
- rtx dest = SET_DEST(set);
-
- // TODO : rewrite to simple return
- std::cerr << "first pseudo: " << FIRST_PSEUDO_REGISTER << '\n';
- //std::cerr << "register: " << REGNO(dest) << "\n";
- //debug(insn);
- // If I understand correctly, global_regs[i] is 1 iff reg i is used
- if (REG_P(dest) && HARD_REGISTER_NUM_P(REGNO(dest))) { // &&
global_regs[REGNO(dest)]
- std::cerr << "sets_global_register: true\n";
- return true;
- }
-
- return false;
-}
-
bool side_effects_with_mem (const_rtx x)
{
const RTX_CODE code = GET_CODE (x);
@@ -1460,10 +1453,7 @@ bool is_rtx_insn_prelive(rtx_insn *insn) {
/* Don't delete insns that may throw if we cannot do so. */
if (!(cfun->can_delete_dead_exceptions && can_alter_cfg) && !insn_nothrow_p
(insn))
return true;
-
- /* TODO : What about call argumets? Accoring to the docs, for function
prologue the RTX_FRAME_RELATED_P
- should return true.
- */
+
/* Callee-save restores are needed. */
if (RTX_FRAME_RELATED_P (insn) && crtl->shrink_wrapped_separate &&
find_reg_note (insn, REG_CFA_RESTORE, NULL))
return true;
@@ -1496,9 +1486,7 @@ bool is_rtx_insn_prelive(rtx_insn *insn) {
// e. g. this one: testsuite/gcc.c-torture/execute/20020418-1.c
// TODO : debug the testcase
// It seems that the issue was due to trap_if rtl insn and fixed with
may_trap_or_fault_p
- // What about can_throw_internal?
- // || can_throw_internal(body) - testy na ntb prochazi
- if (side_effects_with_mem(body)) // || may_trap_or_fault_p(body)) //
replaced by TRAP_IF
+ if (side_effects_with_mem(body)) // may_trap_or_fault_p(body) replaced by
TRAP_IF
return true;
return false;
@@ -1532,8 +1520,7 @@ bool is_prelive(insn_info *insn)
gcc_assert (insn->is_real());
auto rtl = insn->rtl();
- for (auto&& __def : insn->defs()) {
- def_info * def = __def;
+ for (def_info * def : insn->defs()) {
// The purpose of this pass is not to eliminate stores to memory...
if (def->is_mem()) { // TODO : clobbered memory?
return true;
@@ -1541,18 +1528,52 @@ bool is_prelive(insn_info *insn)
gcc_assert(def->is_reg());
// this ignores clobbers, which is probably fine
- if (def->kind() == access_kind::SET
- && (HARD_REGISTER_NUM_P(def->regno())
- || ( pic_offset_table_rtx != nullptr
- && def->regno() == REGNO (pic_offset_table_rtx)
- && REGNO (pic_offset_table_rtx) >= FIRST_PSEUDO_REGISTER))
- ) {
- // TODO : set_noop_p?
-
- // std::cerr << "hard reg marked: " << def->regno() << "in " <<
insn->uid() << "\n";
- // debug(rtl);
+
+
+ // TODO : find something similar to mark_artificial_uses to mark only
+ // artificially-used registers
+ // check: df_get_regular_block_artificial_uses
+ // That should fix following test as assume
+ // gcc.c-torture/execute/20000503-1.c - flags register is unused
+ if (def->kind() != access_kind::SET)
+ continue;
+
+ // This might be messed up a bit
+ if (def->regno() == FRAME_POINTER_REGNUM
+ || def->regno() == STACK_POINTER_REGNUM)
return true;
- }
+
+ // needed by gcc.c-torture/execute/pr51447.c
+ if (HARD_REGISTER_NUM_P (def->regno())
+ && global_regs[def->regno()])
+ return true;
+
+ if (!HARD_FRAME_POINTER_IS_FRAME_POINTER
+ && def->regno() == HARD_FRAME_POINTER_REGNUM)
+ return true;
+
+ if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
+ && fixed_regs[ARG_POINTER_REGNUM]
+ && def->regno() == ARG_POINTER_REGNUM)
+ return true;
+
+ unsigned int picreg = PIC_OFFSET_TABLE_REGNUM;
+ if (picreg != INVALID_REGNUM
+ && fixed_regs[picreg]
+ && def->regno() == picreg)
+ return true;
+
+ // TODO : eh?
+
+ // if (def->kind() == access_kind::SET
+ // && (HARD_REGISTER_NUM_P(def->regno())
+ // || (pic_offset_table_rtx != nullptr
+ // && def->regno() == REGNO (pic_offset_table_rtx)
+ // && REGNO (pic_offset_table_rtx) >= FIRST_PSEUDO_REGISTER))
+ // ) {
+ // // find_reg_note(insn->rtl(), REG_UNUSED, def->regno())
+ // return true;
+ // }
}
return is_rtx_insn_prelive(rtl);
@@ -1582,9 +1603,7 @@ rtl_ssa_dce_prelive(std::unordered_set<insn_info *>
&marked)
rtl_ssa_dce_mark_live(insn, worklist, marked);
}
- // if (insn->can_be_optimized () || insn->is_debug_insn ())
- // if (fwprop_insn (insn, fwprop_addr_p))
- // worklist.safe_push (insn);
+ // Might help to fix -DPREVENT_OPTIMIZATION? (insn->can_be_optimized () ||
insn->is_debug_insn ())
}
return worklist;
@@ -1597,20 +1616,19 @@ rtl_ssa_dce_mark()
// phi insn might have more that one phi node:
gcc/gcc/testsuite/gcc.c-torture/execute/20000224-1.c
std::unordered_set<phi_info *> marked_phi_nodes{};
// Phi will not be prelive
- auto worklist = rtl_ssa_dce_prelive(marked);
- auto_vec<set_info *> worklist_new{};
- for (auto && item : worklist) {
- insn_info * insn = item;
+ auto prelive_insns = rtl_ssa_dce_prelive(marked);
+ auto_vec<set_info *> worklist{};
+ for (insn_info * insn : prelive_insns) {
for (auto&& use : insn->uses()) {
set_info* set = use->def();
if (set) {
- worklist_new.safe_push(set);
+ worklist.safe_push(set);
}
}
}
- while (!worklist_new.is_empty()) {
- set_info* set = worklist_new.pop();
+ while (!worklist.is_empty()) {
+ set_info* set = worklist.pop();
insn_info* insn = set->insn();
if (!insn) {
continue;
@@ -1620,17 +1638,12 @@ rtl_ssa_dce_mark()
* TODO : a phi insn might be visited more times due to having more phi
nodes
* Either we have to mark phi nodes or do not mark phi insn
*/
- // std::cerr << "Current: " << insn->uid() << '\n';
- // if (insn->uid() == -21) {
- // std::cerr << "Insn -21 phi? " << insn->is_phi() << '\n';
- // }
+ auto uid = insn->uid();
if ((marked.count(insn) > 0) && !insn->is_phi()) {
continue;
}
- // std::cout << insn->uid() << " not skipped\n";
-
marked.emplace(insn);
use_array uses = insn->uses();
@@ -1638,6 +1651,7 @@ rtl_ssa_dce_mark()
// Each phi node has a unique uid, yeeey
// So, only one bitmap (with shift) in needed.
phi_info* pi = as_a<phi_info *> (set);
+ auto pi_uid = pi->uid();
if (marked_phi_nodes.count(pi) > 0) {
continue;
}
@@ -1648,22 +1662,16 @@ rtl_ssa_dce_mark()
if (dump_file)
fprintf(dump_file, " Adding insn %d to worklist - mark\n", insn->uid());
- for (auto && use__ : uses) {
- use_info * use = use__;
+ for (use_info * use : uses) {
set_info* parent_set = use->def();
if (!parent_set) {
continue;
}
- worklist_new.safe_push(parent_set);
+ worklist.safe_push(parent_set);
}
}
- // for (auto&& insn : marked) {
- // if (dump_file)
- // fprintf(dump_file, " Marked insn: %d\n", insn->uid());
- // }
-
// TODO : control dependence
return marked;
}
@@ -1671,103 +1679,110 @@ rtl_ssa_dce_mark()
static void
rtl_ssa_dce_sweep(std::unordered_set<insn_info *> marked)
{
- insn_info *next;
- auto_vec<insn_change> to_delete;
- // try to rewrite it with iterator?
// we can get the number of items in the set and create an array of changes
// which will hopefully have constructor for array_slice<insn_info *>
- auto attempt = crtl->ssa->new_change_attempt ();
- // std::cerr << "Change attempt created successfully" << std::endl;
- for (auto && insn : crtl->ssa->all_insns()) {
-
- }
- for (insn_info *insn = crtl->ssa->first_insn(); insn; insn = next)
- {
- if (dump_file)
- {
- fprintf(dump_file, "Insn: %d\n", insn->uid());
- }
- next = insn->next_any_insn();
- if (marked.count(insn) > 0)
- {
+ auto_vec<insn_change> to_delete;
+ for (insn_info * insn : crtl->ssa->all_insns()) {
+ // artificial and marked insns cannot be deleted
+ if (insn->is_artificial() || marked.count(insn) > 0)
continue;
- }
-
+
+ auto change = insn_change::delete_insn(insn);
+ to_delete.safe_push(change);
if (dump_file)
- {
fprintf(dump_file, " Sweeping insn %d\n", insn->uid());
- }
-
- // Skip artificial insns (or uid() < 0)
- if (insn->is_real())
- {
- // std::cerr << "\033[32m" << "Insn: " << insn->uid() << " will be
deleted" << "\033[0m \n";
- auto change = insn_change::delete_insn(insn);
- // crtl->ssa->possibly_queue_changes(change);
- to_delete.safe_push(change);
- // crtl->ssa->change_insn(change);
- }
+ // crtl->ssa->change_insn(change);
}
- // std::cerr << "Selected unmarked insns" << std::endl;
-
+ auto attempt = crtl->ssa->new_change_attempt ();
auto_vec<insn_change*> changes(to_delete.length());
for (size_t i = 0; i != to_delete.length(); ++i) {
changes.safe_push(&to_delete[i]);
}
- // std::cerr << "Verification" << std::endl;
- if (crtl->ssa->verify_insn_changes(changes)) {
- // std::cerr << "Changes are correct" << std::endl;
+ gcc_assert (crtl->ssa->verify_insn_changes(changes));
// segfault: gcc.c-torture/execute/20000224-1.c
- crtl->ssa->change_insns(changes);
- } else {
- // std::cerr << "Changes are not correct\n";
- }
+ crtl->ssa->change_insns(changes);
}
static void
rtl_ssa_dce_transform_insns_to_debug() {
- // TODO : bude nejspise zase treba rozdelit phi a ostatni insns
std::unordered_set<int> is_debug;
+ // TODO : make sure, that phi_nodes have unique id from all insns
+ // Should we use ssa when modifing insns? if yes, we want in-place replace
// chceme prochazet v post orderu, abychom nejdrive zpracovali zavislosti a
pak az definici
// nelze jen menit instrukce, protoze musime informaci propagovat pres phi
node
+ // We check, if insns that use a definition from current insn are all debug
for (insn_info * insn : crtl->ssa->reverse_all_insns()) {
if (insn->is_debug_insn()) { // phi is never debug
// TODO : store info about this insn
-
is_debug.emplace(insn->uid());
continue;
}
if (insn->is_phi()) {
- // TODO : special handling for phi_node required
+ // for each phi_info
+ for (def_info *def : insn->defs()) {
+ phi_info *pi = as_a<phi_info *> (def);
+
+ }
}
- bool is_debug = true;
+ rtx_insn * rtl = insn->rtl();
+ rtx set;
+ if (!(MAY_HAVE_DEBUG_BIND_INSNS
+ && (set = single_set (rtl)) != NULL_RTX
+ && (!side_effects_p (SET_SRC (set))
+ && asm_noperands (PATTERN (rtl)) < 0))) {
+ continue;
+ }
+
+ bool should_be_debug = true;
for (def_info *def : insn->defs()) {
// TODO : how to cast this correctly? - clobber_info
- if (def->mode() == access_kind::CLOBBER)
+ // access_kind for def_insn is only SET or CLOBBER
+ if (def->kind() == access_kind::CLOBBER)
continue;
- set_info* set = as_a<set_info*>(def);
- for (use_info * use : set->all_uses()) {
- auto iii = use->insn()->uid();
+ set_info* si = as_a<set_info*>(def);
+ // TODO : use has_nondebug_uses or has_nondebug_insn_uses - what is the
difference? phi?
+ // after that we will use rtl-ssa change API to make the insn debug (it
will hopefully
+ // recalculate has_nondebug_uses of other instructions...)
+ for (use_info * use : si->all_uses()) {
+ auto iii = use->insn()->is_debug_insn();
}
}
- // TODO : projit vsechny set_infa a podivat se, zda jsou zavisloti jen
debug
- // Musime si dat pozor na phi - tam je treba se podivat na kontretni phi
node
+ if (!should_be_debug) {
+ continue;
+ }
+
+ // TODO : perform a change
+ /* Create DEBUG_EXPR (and DEBUG_EXPR_DECL). */
+ rtx dval = make_debug_expr_from_rtl (SET_DEST (set));
+
+ /* Emit a debug bind insn before the insn in which
+ reg dies. */
+ rtx bind_var_loc =
+ gen_rtx_VAR_LOCATION (GET_MODE (SET_DEST (set)),
+ DEBUG_EXPR_TREE_DECL (dval),
+ SET_SRC (set),
+ VAR_INIT_STATUS_INITIALIZED);
+
+ rtx_insn * bind = emit_debug_insn_before (bind_var_loc, rtl);
+ // auto debug_insn = insn_info(insn->bb(), bind, 0);
+ auto attempt = crtl->ssa->new_change_attempt ();
+ auto change = insn_change(insn);
+ // TODO : delete rtx from cfg and replace insn in ssa to debug_insn
+ // delete_insn_and_edges or delete_insn - do we need to delete edges?
}
}
static void
rtl_ssa_dce_init()
{
- // internal compiler error: gcc.c-torture/execute/20040811-1.c -
rtl_ssa::function_info::add_phi_nodes
-
calculate_dominance_info(CDI_DOMINATORS);
- // here we create ssa form for function
+ // internal compiler error: gcc.c-torture/execute/20040811-1.c -
rtl_ssa::function_info::add_phi_nodes
crtl->ssa = new rtl_ssa::function_info(cfun);
}
@@ -1788,34 +1803,29 @@ rtl_ssa_dce_done()
static unsigned int
rtl_ssa_dce()
{
- rtl_ssa_dce_init();
- std::cout << "\033[31m" << "SSA FOR DCE PASS:" << "\033[0m" << "\n";
- debug(crtl->ssa);
- std::cout << "\033[31m" << "Before rtl ssa dce pass" << "\033[0m" << "\n";
-
- // for (rtx_insn * insn = get_insns (); insn != nullptr; insn =
next_insn(insn)) {
- // debug(insn);
+ // for (int i = 0; i < FIRST_VIRTUAL_REGISTER; ++i) {
+ // if (global_regs[i] > 0)
+ // std::cerr << "Global reg needed: " << i << '\n';
+ // if (fixed_regs[i] > 0)
+ // std::cerr << "Fixed reg: " << i << '\n';
// }
-
- // std::cout << "\033[31m" << "Before rtl ssa dce pass end" << "\033[0m" <<
"\n";
-
-
+ // std::cerr << "RTL SSA BEGIN\n" << std::endl;
+ rtl_ssa_dce_init();
std::unordered_set<insn_info *> marked = rtl_ssa_dce_mark();
rtl_ssa_dce_sweep(marked);
+ // std::cerr << "\033[31m" << "SSA debug start" << "\033[0m" << "\n";
+ // debug (crtl->ssa);
+ // for (insn_info * insn : crtl->ssa->all_insns()) {
+ // if (insn->is_artificial())
+ // continue;
+ // debug(insn->rtl());
+ // }
+ // std::cerr << "\033[31m" << "SSA debug end" << "\033[0m" << "\n";
rtl_ssa_dce_done();
- // std::cout << "\033[32m" << "After rtl ssa dce" << "\033[0m" << "\n";
- // for (rtx_insn * insn = get_insns (); insn != nullptr; insn =
next_insn(insn)) {
- // debug(insn);
+ // if (delete_trivially_dead_insns(get_insns (), max_reg_num ())) {
+ // std::cerr << "\033[31m" << "rtl_ssa_dce did not delete everything :("
<< "\033[0m" << "\n";
// }
- if (delete_trivially_dead_insns(get_insns (), max_reg_num ())) {
- std::cout << "\033[31m" << "Some insns deleted by
delete_trivially_dead_insns" << "\033[0m" << "\n";
- // for (rtx_insn * insn = get_insns (); insn != nullptr; insn =
next_insn(insn)) {
- // debug(insn);
- // }
- std::cerr << "\033[31m" << "rtl_ssa_dce did not delete everything :(" <<
"\033[0m" << "\n";
- }
- // std::cout << "rtl ssa dce FINISH\n";
return 0;
}
diff --git a/gcc/passes.def b/gcc/passes.def
index f90a15bf7ddf..2509f44bc5c7 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -459,7 +459,6 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_lower_subreg);
NEXT_PASS (pass_df_initialize_opt);
NEXT_PASS (pass_cse);
- NEXT_PASS (pass_rtl_ssa_dce);
NEXT_PASS (pass_rtl_fwprop);
NEXT_PASS (pass_rtl_cprop);
NEXT_PASS (pass_rtl_pre);
@@ -489,6 +488,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_rtl_fwprop_addr);
NEXT_PASS (pass_inc_dec);
NEXT_PASS (pass_initialize_regs);
+ NEXT_PASS (pass_rtl_ssa_dce);
NEXT_PASS (pass_ud_rtl_dce);
NEXT_PASS (pass_ext_dce);
NEXT_PASS (pass_combine);
@@ -533,6 +533,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_fold_mem_offsets);
NEXT_PASS (pass_cprop_hardreg);
// NEXT_PASS (pass_rtl_ssa_dce);
+ // NEXT_PASS (pass_fast_rtl_dce);
NEXT_PASS (pass_reorder_blocks);
NEXT_PASS (pass_leaf_regs);
NEXT_PASS (pass_split_before_sched2);
